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System Engineering Experiences

System Engineering Experiences. Harold Sasnowitz, IEEE Life Senior Member. Agenda. Angle Rate Bombing System Space Shuttle Harpoon Missile Airborne Mine Countermeasures. US Navy Angel Rate Bombing System (ARBS). Purpose: precision bombing using horizontal flight path Circa 1975

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System Engineering Experiences

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  1. System Engineering Experiences Harold Sasnowitz, IEEE Life Senior Member

  2. Agenda • Angle Rate Bombing System • Space Shuttle • Harpoon Missile • Airborne Mine Countermeasures

  3. US Navy Angel Rate Bombing System (ARBS) • Purpose: precision bombing using horizontal flight path • Circa 1975 • Computer Interface: discretes, Direct memory access, interrupts, serial and parallel channels • Processor: SP-1, two page processor • Radar image projected onto HUD; Pilot places crosshairs on target and computer determines release point • Problem posed as three DMA channels, always in particular order • Initial testing resulted in system failure: HUD blanks when system engaged • Finding: DMA channel order different than discussed

  4. Space Shuttle • System description • Requirement: survive two like failures • Five general purpose computers, all executing identical software • All sensors and flight effectors fault tolerant and multiple copies • All 5 computers receive all data input • All 5 computers receive output data from the other 4 computers and “fail votes”

  5. First Flight Failure • First flight not vertical launch • Drop from Shuttle Carrier Aircraft • Shuttle and Carrier held together with pyro bolts • At separation “GPC 2 light” • Studied System Services software • “All leaves cancelled” • Lost Weekend to engineering staff • Bad solder joint on a computer card

  6. Shuttle Reliability Study • Purpose: Recommend flight rules for mission abort due to computer system failures • Method: Determine reliability of Shuttle computer system • Reliability at time t is probability system will be working at time t • For components: R=e-λt • What is λ? Failure rate in failures per million hours • For system: R=∫e-λtdt • What is λ for a system?

  7. System State Space Diagram 4/1 λ λ 4/0 3/1 λ λ λ λ 3/0 3/0 λ λ Vehicle loss

  8. What is system λ? λ11

  9. For system: R=∫e-λtdt • Solution is alternating infinite sum • Programmed in APL

  10. US Navy Harpoon Anti-ship Missile • Circa 1971 • Mid-course Guidance Unit (MGU) • One card, 250 kops; 8K core memory • For tracking location of self contains Attitude Reference Assembly • Contains 3 gyros and 3 accelerometers • ARA interface to counters in computer • Present position provided by launch computer • Target location determined and provided by on-board radar • 50 msec hardware timer interrupt causes software interrupt • Handler to reads counters • Initial testing showed g slightly high • 50 msec counter off by one

  11. Black System

  12. US Navy Airborne Mine Countermeasures • Initial Deployment Now • Purpose: find and destroy shallow and deepwater mines • Sensors controlled from console on-board MH-60S • Numerous tests required to qualify equipment beyond performing basic function • Temperature, humidity, salt spray, electromagnetic compatibility, others • Coordinating scheduling of production, factory flight testing, Navy operational testing complex

  13. When Unanticipated Things Occur • Operational testing requires: test range, pilots, maintenance group, hangars • Fire occurred during EMC testing of one console • Unit involved in fire became “hangar queen” • Entire test schedule impacted

  14. US Air Force B-2 Stealth Bomber

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